1. Field of the Invention
In one of its aspects, the invention relates to a process for the recovery of heavy minerals from tar sands or a feedstock derived from tar sands. More particularly, the invention relates to a process for the separation of bitumen from the heavy minerals component of the tar sands or a feedstock derived from tar sands.
2. Description of the Prior Art
Extensive deposits of tar sands, bituminous sands, bituminous diatomite and similar materials are known to exist throughout the world. These materials comprise a siliceous matrix of sands, sandstones or diatomaceous earth, which is coated or saturated with relatively high molecular weight hydrocarbon materials. These deposits are generally located at or near the Earth's surface, although some deposits may be buried by as much as two thousand feet of overburden. It has been estimated that the reserves of petroleum products recoverable from the known deposits of tar sands would be approximately equivalent to the worldwide reserves estimated for conventional crude oil.
As mined, the tar sands are present in general as agglomerates or lumps comprising sand, clay, water and viscous hydrocarbonaceous material called bitumen.
The predominating mineral component of the material as mined is, in most cases, as quartz sand. Typically, the quartz sand is surrounded by bitumen in quantities of in the range of from about 5 to about 20 or more weight percent of the total composition. In addition, tar sands generally also contain colloidal (˜2 μm diameter) material, usually referred to as colloidal clay since it contains silica and alumina, in quantities of from about 1 to about 50 weight percent of the total composition.
It is known that the bitumen may be upgraded to a hydrocarbon material of lower molecular weight, in particular to a hydrocarbon material that is liquid at room temperature.
Several methods have been developed for purifying tar sands to provide bitumen concentrates that can be used as feedstock for further upgrading to produce useful products. The principal purification technique which has been applied to tar sands in order to concentrate bitumen therefrom is extraction. One type of extraction conventionally used is known as the “hot water” process. In the “hot water” process, advantage is taken of the fact that tar sands produce bituminous slurry when mulled with hot water and sodium hydroxide. The bituminous slurry is recovered, treated with a hydrocarbon diluent, and then subjected to a centrifugation process that yields a tailings comprising heavy minerals to which some of the bitumen remains adhered.
It is known to further treat the tailings to separate the bitumen from the heavy minerals to improve the purity of heavy minerals. Specifically, it is conventional to subject the tailings to high temperature roasting to “bum off” the bitumen from the heavy minerals. Unfortunately, the high temperature roasting is cost intensive and effects removal of the bitumen at the expense of erasing the magnetic contrast between the remaining heavy minerals. The lack of magnetic contrast hinders separation of valuable minerals, such as titanium (e.g., TiO2), from gangue materials.
Notwithstanding the advances made in the art to date, there is still room for improvement. For example, there is still a need in the art for an efficient process for recovery of valuable minerals (such as minerals of titanium) from a tar sands starting material or a feedstock derived from tar sands. It would be advantageous if such a process were relatively low cost to implement and practice.